Circuit interrupters are electrical components that are used to open an electrical circuit, interrupting the flow of current. A basic example of a circuit interrupter is a switch, which generally consists of two electrical contacts in one of two states; either closed, meaning that the contacts are in electrical contact with each other allowing electricity to flow between them, or open, meaning that the contacts are not in electrical contact with each other preventing the flow of electricity. A switch may be directly manipulated to provide a control signal to a system, such as a computer keyboard button, or to control power flow in a circuit, such as a light switch.
Another example of a circuit interrupter is a circuit breaker. A circuit breaker may be used, for example, in an electrical panel to limit the amount of current flowing through the electrical wiring. A circuit breaker is designed to protect an electrical circuit from damage caused by, for example, an overload, a ground fault or a short circuit. If a fault condition, such as a power surge occurs in the electrical wiring, the breaker will trip. This will cause a breaker that was in an “on” position to flip to an “off” position and interrupt the flow of electrical power through the breaker. Circuit breakers are generally provided to protect the electrical wiring by limiting the amount of current transmitted through the wires to a level that will not damage them. Circuit breakers can also prevent destruction of the devices that may draw too much current.
A standard circuit breaker has a terminal connected to a source of electrical power, such as a power line electrically connected to the secondary of a power company transformer, and a second terminal electrically connected to the wires that the breaker is intended to protect. Conventionally, these terminals are referred to as the “line” and “load” respectively. The line is sometimes referred to as the input of the circuit breaker. The load is sometimes referred to as the output of the circuit breaker, which connects to the electrical circuit and components receiving the electrical power.
An individual protected device, such as a single air conditioner, may be directly connected to a circuit breaker. Alternatively, circuit breakers may also be used to protect the wiring feeding multiple devices that may be connected to the circuit via various electrical outlets (e.g., various devices in a room each plugged into an outlet all on the same circuit fed by the same circuit breaker).
A circuit breaker can be used as a replacement for a fuse. Unlike a fuse however, which typically operates to open in an over current situation and then must be replaced; a circuit breaker can be “reset” (either manually or automatically) to resume operation. Fuses perform a similar role to circuit breakers, however, circuit breakers are easier to use and typically safer to service and operate.
Unlike the situation when a fuse blows, when a circuit breaker trips, it is relatively easy to determine which circuit breaker feeds the interrupted circuit by looking at the electrical panel and noting which breaker has a handle in the “tripped” position. This breaker can then be simply moved to the “off” position (which resets the circuit breaker), and then moved to the “on” position and power will resume.
In general, a single pole circuit interrupter has two contacts positioned inside of a housing. The first contact is stationary and may be connected to either the line or the load. The second contact is movable with respect to the first contact, such that when the circuit breaker is in the “off” or “tripped” position, a gap exists between the first and second contact.
A problem with the above-described circuit interrupters arises when energized contacts are opened while under load. As the contacts separate, transitioning from a closed to an open position, or when the opposite occurs, an electric arc may be formed in the gap between the contacts. An electrical arc is a plasma discharge between two points that is caused by electrical current that ionizes gasses in the air between the two points.
The creation of an arc during transition of the contacts can result in undesirable effects that negatively affect the operation of the circuit interrupter, even potentially creating a safety hazard. These negative effects can also have adverse consequences on the functioning of the circuit interrupter.
One possible consequence is that the arc may short to objects inside the circuit interrupter and/or to surrounding objects, causing damage and presenting a potential fire or safety hazard.
Another consequence of arcing is that the arc energy damages the contacts themselves, causing some material to escape into the air as fine particulate matter. The debris that has been melted off of the contacts can migrate or be flung into the mechanism of the circuit interrupter, destroying the mechanism or reducing its operational lifespan.
Still another effect of arcing is due to the extremely high temperature of the arc (tens of thousands of degrees Celsius), which can impact the surrounding gas molecules creating ozone, carbon monoxide, and other dangerous compounds. The arc can also ionize surrounding gasses, potentially creating alternate conduction paths.
Because of these detrimental effects it is very important to quickly suppress or quench the arc to prevent the above-described situations. Various techniques for improved arc quenching are known. For example, U.S. Pat. Nos. 8,822,866 and 8,866,034 assigned to Carling Technologies, Inc., variously relate to the use of an electromagnetic field to guide an arc toward an arc splitter.
However, generating an electromagnetic field to move an arc requires the use of power, and generates heat in the device. In order to avoid these negative issues, it has been conceived to incorporate a permanent magnet into the circuit interrupter, which produces a magnetic field without requiring a supply of electricity. However, permanent magnets produce a magnetic field having a fixed direction with respect to the magnet. Thus, known solutions for guiding an arc into an arc path using a permanent magnet are circuit polarity dependent. This is due to the fact that a magnetic field produced by a fixed permanent magnet has a fixed direction. As such, the mechanism for magnetically guiding the arc into the path depends upon the direction the current is flowing through the circuit interrupter.
U.S. Patent Application Publication No. 2013/0313228 (the '228 application) is directed to a switch including two sets of contacts in series that are designed to be used with D.C. voltage where an arc that occurs between either set of contacts will be disapated regardless of the polarity of the D.C. voltage. The '228 application teaches that “the magnets are always arranged in opposing pairs, in order to be able to generate a homogeneous magnetic field perpendicular to the current direction through the arcs and perpendicular to the arc deflector plates, contact deflector plates and bridge plates.” [0027]. Accordingly, the '228 application requires the use of two pairs of relatively large plate-type magnets as well as the specific configuration for the “arc deflector plates” and “contact deflector plates.” This results in a fairly large and bulky arraignment, which requires additional materials increasing the cost of the device.
U.S. Pat. No. 9,406,465 (the '465 patent) is also focused on providing a circuit interrupter having an arc extinguisher that functions to arrest an arc between the circuit interrupter contacts regardless of the polarity of the circuit. In particular, the '465 patent discloses that this is achieved by placing a permanent magnet such that if an arc develops, the arc is driven into a first arc path when a polarity of the first contact is positive and the arc is driven into a second arc path when a polarity of the first contact is negative. However, the '465 patent also includes embodiments where a set of magnets are positioned laterally to the set of contacts as disclosed in the '228 application. In one embodiment, the '465 patent discloses a single magnet that is positioned below the stationary contact, but again, while effective in driving and arc that may develop, the magnet is relatively large in size in order to generate the magnetic field to drive and arc.
It is therefore desired to provide arc quenching usable with a circuit interrupter that overcomes the above-described limitations.